1. Field of the Invention
The present invention relates to a disc recliner for a vehicle seat assembly that allows pivotal adjustment of a seat back relative to a seat cushion. More particularly, the present invention relates to a disc recliner having internal leaf springs providing an actuation torque that remains relatively constant or decreases as the disc recliner is actuated to allow pivotal movement of a seat back relative to a seat cushion.
2. Description of Related Art
Automotive vehicles typically include one or more seat assemblies having a seat cushion and a seat back tar supporting passengers above a vehicle floor. The seat assembly is commonly mounted to the vehicle floor by a seat track assembly for providing fore and aft adjustment of the seat assembly for passenger comfort. The seat back is typically pivotally coupled to the seat cushion by a recliner assembly for providing pivotal adjustment of the seat back relative to the seat cushion.
It is common that the recliner assembly includes a pair of spaced apart disc recliners that operatively couple the seat back to the seat cushion. A typical disc recliner generally includes a fixed plate secured to the seat cushion and a movable plate secured to the seat back and rotatably coupled to the fixed plate. The disc recliner also includes a locking mechanism to secure the movable plate to the fixed plate thereby maintaining the seat back in a reclined seating position. One type of locking mechanism includes one or more pawls with each pawl having a plurality of teeth. The pawls are movable, either slidably or pivotally, in a radial direction between a locked position and an unlocked position. With the pawls in the locked position, the teeth on the pawls are engaged with an annular rim of teeth on the movable plate, thus locking the seat back relative to the seat cushion. With the pawls in the unlocked position, the teeth on the pawls are disengaged from the annular rim of teeth on the movable plate, thus allowing pivotal adjustment of the seat back relative to the seat cushion between a plurality of reclined seating positions.
The pawls are typically spring biased to the locked position through a cam that is mounted on a shaft. An actuation torque is applied to rotate the shaft and overcome the spring bias, which allows the pawls to move from the locked position to the unlocked position. However, as the shaft is rotated, the spring bias and torque increases such that the actuation force to unlock the disc recliner may become undesirable.
It is desirable, therefore, to provide a disc recliner which is spring biased to a locked condition wherein the actuation force is controlled to prevent undesirable operating efforts.